I have acquired a 20W solar panel that shows 20vdc when not connected to anything (in full sun). When hooked up to a 12v battery, I have seen it as high as 17vdc. I'm wondering if I can get away with hooking this up to my RV to help keep the batteries (currently 2 12v, soon to be replaced with 2 6v) topped off while in storage, without needing a charge controller? Although the voltage is high, the amperage is pretty low. Will a 1 amp charge at 17 vdc hurt my batteries?

No, a 1amp charge is barely a trickle.....likely won't maintain your batteries in storage unless battery disconnect is on....

You may as well just disconnect them.

Rule of thumb is that if the charge current is less than 1% of the AH capacity then no charge controller is needed. That means your fine since you've most certainly got more AH capacity than that.Don't expect that little panel to do much. Sounds like it was free so might as well give it a shot.

Yup, it was a freebie. And yes, I disconnect my batteries when in storage. I was just concerned with the 17+ volts, but at only 1 amp, I guess it should be fine.

4x4van wrote: Will a 1 amp charge at 17 vdc hurt my batteries?YES. Over a long period it might.Maybe as little as a few weeks.You NEED a controller.1 amp will slowly charge the batteries.As the battery charge (voltage) goes up, so will the charger voltage.....maybe as high as 20 volts and it still will push an amp or more.Using it for very long without a controller might not be much of a risk but it is a small one......especially if you have wet cell batteries.

20W solar...need controller? | Good Sam Community

29 Replies

3_tons
Explorer III
May 02, 2019
2112 wrote:
You could use something like THIS and a diode between the panel and battery. Adjust it to 13.2V or so at the battery.

This is a very creative idea!!
jplante4
Explorer II
May 02, 2019
Moved from General RVing
2112
Explorer II
May 02, 2019
You could use something like THIS and a diode between the panel and battery. Adjust it to 13.2V or so at the battery.
time2roll
Nomad
May 02, 2019
17 volts every day in storage is too high. Keep an eye on it and start looking for a controller.
Sam_Spade
Explorer
May 02, 2019
4x4van wrote:
Will a 1 amp charge at 17 vdc hurt my batteries?

YES. Over a long period it might.
Maybe as little as a few weeks.
You NEED a controller.

1 amp will slowly charge the batteries.
As the battery charge (voltage) goes up, so will the charger voltage.....maybe as high as 20 volts and it still will push an amp or more.

Using it for very long without a controller might not be much of a risk but it is a small one......especially if you have wet cell batteries.
4x4van
Explorer III
May 01, 2019
Yup, it was a freebie. And yes, I disconnect my batteries when in storage. I was just concerned with the 17+ volts, but at only 1 amp, I guess it should be fine.
KD4UPL
Explorer II
May 01, 2019
Rule of thumb is that if the charge current is less than 1% of the AH capacity then no charge controller is needed. That means your fine since you've most certainly got more AH capacity than that.
Don't expect that little panel to do much. Sounds like it was free so might as well give it a shot.
2oldman
Explorer II
May 01, 2019
You may as well just disconnect them.
Ed_Gee
Explorer II
May 01, 2019
No, a 1amp charge is barely a trickle.....likely won't maintain your batteries in storage unless battery disconnect is on....

Forum Discussion

20W solar...need controller?

29 Replies

About Technical Issues

Related Content

Sway Control

20W solar...need controller?

Need Solar Guru Help!

Solar Charge Controller Advice Needed

Solar charge controller selection help needed